The invention relates to a network connection system for communicating between hosts of a computer network constructing an internet and to a connection substitute correspondence client. More particularly, the invention relates to a network connection system in which a communication from a host out of an organization to a host which doesn""t have a formal IP address is smoothly progressed by a substitute connection and to a connection substitute correspondence client.
In the recent rapid development of the internet, a problem such that the number of IP addresses [internet protocol addresses: hereinafter, referred to as xe2x80x9cformal addressesxe2x80x9d] lacks due to an increase in number of hosts is becoming serious. It is presumed that it is difficult to connect the host to the internet and to participate in the internet of the organization. A method of solving it is required. Actually, in the organization in which the number of formal addresses lacks, informal addresses which are not formally allocated and local addresses (private addresses of the reference standard RFC1597 of the internet) which can be used only in the organization are allocated to the hosts in the organization. However, the hosts which don""t have the formal addresses cannot directly communicate with the host which has the formal address and which is connected to the internet. Therefore, a network connection system having a connection substitute server is provided in order to enable a communication between a host which doesn""t have the formal address and which belongs to the first organization (hereinafter, such a host is referred to as an xe2x80x9cintra-organization hostxe2x80x9d) and a host which has a formal address and which belongs to the second organization different from the first organization (hereinafter, such a host is referred to as an xe2x80x9cout-of-organization hostxe2x80x9d). The connection substitute server is generally realized by a server called an xe2x80x9capplication gateway serverxe2x80x9d. In the network connection system, the connection substitute server having the formal addresses is located at a position where it can be accessed from both of the host which doesn""t have the formal address in the organization and the host having the formal address out of the organization, ordinarily, at a position near a relay point between the intra-organization and the out-of-organization. When a communication request of the host in the organization is received, the connection substitute server accesses to the host out of the organization in place of the host in the organization. In this case, it is necessary for the user to prepare a client software of the connection substitute server correspondence and to previously designate the connection substitute server to be used.
Hitherto, in the network connection system such as Socks Protocol Version 4.4 of the INTERNET-DRAFT (draft before it becomes the reference standard RFC), CERN httpd proxy, or the like, the system mainly corresponds to a connection request from the intra-organization to the out-of-organization. Namely, when a connection from the intra-organization to the out-of-organization is requested, the host having the informal address or local address in the organization requests a retrieval of addresses to a name server in which the hosts having formal addresses have already been registered by designating a host name. Subsequently, the host having the informal address or local address presents the formal address obtained from the name server by the retrieval and requests for the connection substitute to the connection substitute server which has been preset in a connection substitute correspondence client. In this instance, there is a prerequisite such that the connection request source is the intra-organization host (host of the first organization) having the informal address or local address and the connection destination is the out-of-organization host (host of the second organization different from the first organization) having the formal address. Therefore, the address of the connection destination is unique and can specify the host. So long as there is at least one connection substitute server, it is possible to communicate with the host having the formal address in the world. Therefore, it is; sufficient that the connection substitute server which is used by himself is fixedly set as a correspondence client of the connection substitute server.
In such a conventional network connection system, however, on the contrary, for a connection request from out-of-organization to the intra-organization, there is a prerequisite such that the connection request source is the host having the formal address out of the organization and the connection destination is the host having the informal address or local address in the organization which cannot be used in a place out of the organization. Therefore, the address of the host of the connection destination is not unique and there is a possibility such that the same address is used in a plurality of different organizations. Thus, the host of the connection destination cannot be specified by the informal address or local address indicative of the connection destination. Therefore, the connection substitute server having the formal address of the organization to which the connection destination host having only the informal address or local address belongs has to be preset on the connection request source side. Therefore, when it is intended to communicate with the host which doesn""t have the formal address and which belongs to another organization, there occurs a problem such that the informal address or local address of the host to be connected and the formal address of the connection substitute server of the organization to be connected have to be manually examined and the formal address of the connection substitute server has to be reset each time by a partner destination to be connected.
According to the invention, there are provided a network connection system and a connection substitute correspondence client, in which a connection to a host which belongs to another organization and which doesn""t have a formal address is automatically established by a simple connection request such as to present only a host name, thereby enabling a communication with the host which belongs to such another organization and which doesn""t have the formal address to be performed.
First, a network connection system of the invention has a connection substitute server which is generally called an xe2x80x9capplication gateway serverxe2x80x9d. The connection substitute server substitutes the connection between a host machine having an informal address that is not formally allocated or a local address that is used in the organization and doesn""t flow path information to the outside and a host machine which has the formal address and which is out of the organization and the server relays. The network connection system of the invention has a name server. A correspondence relation between the host machine which doesn""t have the formal address and the connection substitute server has previously been registered as connection substitute server information in the name server. Further, the network connection system of the invention has a connection substitute correspondence client. When a communication request in which a host name of a connection request destination has been designated is received, the connection substitute correspondence client requests the name server to retrieve the connection substitute server information and also requests the connection substitute server recognized from the retrieval result to substitute the connection with the host machine having the informal address or local address of the connection request destination. According to such a construction, the connection to the host machine which belongs to another organization and doesn""t have the formal address is enabled. The address information is registered into the name server in correspondence to the host name. When the address information doesn""t indicate the formal address, namely, in case of the informal address or local address, the allocated connection substitute server information is registered. As such connection substitute server information, there are a host name and a formal address of the connection substitute server. For example, as a formal address, an IP address of an internet protocol network is registered in the name server. The connection substitute correspondence client has: a retrieving mechanism for requesting the name server to retrieve by a communication request; a control mechanism for instructing a connection with the connection request destination on the basis of the retrieval result from the name server received by the retrieving mechanism; and a connecting mechanism for connecting with the connection request destination on the basis of a connecting instruction of the control mechanism. In this case, when the registration of the formal address of the connection request destination is recognized by the retrieval of the name server, the control mechanism of the connection substitute correspondence client instructs the connecting mechanism to connect with a machine having the formal address of the connection request destination. When the registration of the connection substitute server information of the connection request destination is recognized by the retrieval of the name server, the control mechanism of the connection substitute correspondence client instructs the connecting mechanism to connect with the recognized connection substitute server. On the other hand, when neither the registration of the formal address of the connection request destination nor the registration of the connection substitute server information can be recognized by the retrieval of the name server, the control mechanism of the connection substitute correspondence client notifies of a connection error and finishes the processes.
Further, the network connection system of the invention provides a form of the connection substitute correspondence client when presuming a case where the informal addresses are abandoned and only the local addresses (including the private address of RFC1597) are used. The form of the connection substitute correspondence client comprises: an address retrieving mechanism for requesting the name server to retrieve address information of a connection request destination by a communication request; a local address judging mechanism to judge whether the address information registered in the name server by the retrieval of the address retrieving mechanism is a local address or not; a connection substitute server retrieving mechanism for requesting the name server to retrieve substitute server information when the registration of the local address is judged by the local address judging mechanism; a control mechanism for instructing a connection with the connection request destination on the basis of a judgment result of the local address judging mechanism and a retrieval result of the connection substitute server retrieving mechanism; and a connecting mechanism for connecting with the connection request destination on the basis of the connecting instruction of the control mechanism. Namely, the connection substitute correspondence client executes the retrieval of the name server of two stages such that the address information is first retrieved from the host name of the connection request destination and, when the local address is judged, the connection substitute server information is retrieved. In the retrieval at two stages, when the local address judging mechanism judges the registration of the formal address of the connection request destination by the retrieval of the name server by the address information retrieving mechanism, the control mechanism of the connection substitute correspondence client instructs the connecting mechanism to connect with a machine of the connection request destination having the formal address. In this case, when the address information is not registered for the retrieval of the name server by the address retrieving mechanism, a connection error is notified and the processes are finished. On the basis of the judgment result of the local address, when the registration of the connection substitute server information of the connection request destination is recognized by the retrieval of the name server by the connection substitute server retrieving mechanism, the control mechanism of the connection substitute correspondence client instructs the connecting mechanism to connect with the recognized connection substitute server. In this case, when the connection substitute server information is not registered for the retrieval of the name server by the connection substitute server retrieving mechanism, a connection error is notified and the processes are finished.
Further, according to the invention, the connection substitute correspondence client itself which is used in the network connection system is provided. In response to a communication request in which a host machine having no formal address in the organization is set to a connection request destination, the connection substitute correspondence client requests the name server to retrieve the connection substitute server for substituting the connection with the host machine having the formal address out of the organization and for relaying, requests the connection substitute server recognized from the retrieval result to execute the connection substitute with the host machine of the connection request destination, and enables the connection to the host machine which belongs to another organization and which doesn""t have the formal address. The other feature of the connection substitute correspondence client is fundamentally the same as that of the network connection system.
As a modification of the network connection system of the invention, in addition to the connection substitute server for substituting the connection between the host machine belonging to the first organization and the host machine which doesn""t have the formal address and which belongs to the second organization different from the first organization and for relaying, there are provided: a first name server in which a correspondence relation between the host machine having no formal address and the connection substitute server has previously been registered as connection substitute server information; and a second name server in which a correspondence relation between the host name of the host machine which belongs to the second organization and which doesn""t have the formal address in the second organization and the informal address or local address of the host machine has previously been registered as informal/local address information. In this case, in response to a communication request in which the host name of the connection request destination has been designated, the connection substitute correspondence client requests the first name server to retrieve the connection substitute server information, presents the host name of the host machine of the connection request destination to the connection substitute server recognized from the retrieval result, and requests such a server to execute the connection substitute. Therefore, on the basis of the connection substituting request by the presentation of the host name from the connection substitute correspondence client, the connection substitute server requests the second name server to retrieve the informal/local address information by the host name, and substitutes the connection between the host machine of the connection request destination recognized from the retrieval result and the connection substitute correspondence client.
According to such a network connection system and a connection substitute correspondence client of the invention, when the user who uses the host (client in the present invention) belonging to the first organization requests a connection with the host which belongs to the second organization as another organization and which has an informal address or local address in the second organization, a connection request in which the host name of the connection request destination has been designated is executed to the connection substitute correspondence client. In response to the connection request, a retrieval of the connection substitute server information using the host name is requested to the name server. The informal address or local address of the connection request destination and the host name and formal address of the connection substitute server are confirmed. When there is a registration of them, a connection substitute to the host in the organization is requested to the registered connection substitute server and a communication with the host having no formal address can be performed.
When the informal addresses are not generally used and addresses which are used in the organization are only the local addresses, when receiving the connection request from the host out of the organization, the connection substitute correspondence client first retrieves the name server to see whether the address information that is designated by the host name has been registered or not. By the address retrieval, only when the registered address is the local address, the retrieval of the connection substitute server information is requested to the name server. The connection substitute to the host in the organization is requested to the registered connection substitute server. A communication with the host having the local address is executed. Therefore, the unnecessary retrieval of the connection substitute server information for the name server when the registered address is not the local address can be prevented.
The above and other objects, features, and advantages of the present invention will become more apparent from the following detailed description with reference to the drawings.